Mosquito season in Lyon County, IA: when it starts and ends
Mosquito months in Lyon County
In a normal year mosquito season in Lyon County, IA starts around April 25 and ends around October 12, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Lyon County, and when
- Start tipping out standing water weekly by April 11.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 12.
- 19 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check IA spray notices.
Lyon County against the rest of IA
Lyon County has the 86th longest season of 99 IA counties, at 170 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 45.9°F.
- Hamilton County: April 24 to October 12 (171 days, 0 WNV)
- Benton County: April 25 to October 12 (170 days, 0 WNV)
- Kossuth County: April 26 to October 12 (170 days, 3 WNV)
- Cerro Gordo County: April 25 to October 11 (169 days, 0 WNV)
West Nile in Lyon County
From 1999 to 2025, CDC ArboNET counted 31 human West Nile cases in Lyon County (14 neuroinvasive) across 11 years. The worst was 2018 with 8; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.